Radiation

Which of the following is correct for a black body?

The sum of absorptance, transmittance and reflectance of a body is equal to ____.

For a perfectly black body the reflectance and transmittance is equal to one.

Write the SI unit of radiant emitance.

Total radiant emitance is the power radiated by the whole surface of a body.

Total radiant emittance is a unit less quantity.

What is the SI unit of total exitance?

Write the unit of absolute emissivity.

Reflectivity and transmissivity of a black body is equal to one.

Define total absorptivity.

Define radiant exitance.

What do you understand by the term total radiant exitance?

What do you understand by absolute emissivity.

What do you understand by total absorptivity of a material?

What is the spectral absorptive power?

Scientists have made a light source whose spectral emissive power $\frac{dI}{d\lambda }$ is constant over the visible range. Here $I$ is intensity and $\lambda$ is the wavelength. In other words, $\frac{dI}{d\lambda }$ graph is shown below. This beam of area $1 {\mathrm{m}}^2$ is incident on the emitter plate of the photoelectric tube. The collector plate is sufficiently positive so that tube is in saturation mode. Assume that each capable photon liberates $1$ electron. If work function is $2 \mathrm{eV},$ what is the current (in $\mathrm{A}$) in the tube? Round off to the nearest integer.

Which of the following is the effect of heating?

Explain athermanous medium with an example.

What is diathermanous medium?

No medium is required for transfer of heat by the process of thermal _____.